Emulsion polymerization of gaseous tetrafluoroethylene (TFE) or its copolymers is known. Aqueous colloidal dispersions of PTFE or TFE comonomer systems can be prepared in a pressure reactor by placing gaseous TFE monomer, or a mixture of it and comonomers in contact with an aqueous solution containing at least one emulsifier which generally is a fluorinated surfactant, possibly a buffer for keeping the medium at a given pH, and at least one initiator capable of forming free radicals at the polymerization temperature. The free radical initiators are usually water soluble peroxides, or alkaline or ammonium persulfates. Persulfate can be used alone if the polymerization temperature is above approximately 50.degree. C., or in association with a reducing agent such as ferrous salt, silver nitrate, or sodium bisulfite if the polymerization temperature is approximately between 5.degree. to 55.degree. C., as described in the U.S. Pat. No. 4,384,092. The fluorinated surfactants can be anionic, cationic, or nonionic surfactants that possess fluorine atoms and possibly chlorine or hydrogen atoms. However, the most commonly used surfactants are the salts of perfluorinated carboxylic acids or the salts of perfluorinated sulfonic acids. The gaseous monomer molecules enter the aqueous liquid and react to form polymer without first forming a distinct liquid phase.
Emulsion polymerization of tetrafluoroethylene in general produces colloidal particles in the shape of spherical, ellipsoidal, rod-like, or sometimes needle like. The colloidal particles produced by conventional methods are all in a distinct domain (discontinuous) where the aqueous phase is continuous.